Cancer/tumor is a major cause of morbidity in the United States, and the mortality rate of several cancer types is increasing. Cancer cells share the characteristics of disordered control over normal cell division, growth, and differentiation. The initial clinical manifestations of tumor are extremely heterogeneous, with over 70 types of cancer occurring in virtually every organ and tissue of the body. Some of those classified cancer types may represent different molecular diseases. Unfortunately, some cancers may be asymptomatic until late in the disease course, when treatment is more difficult, and prognosis is considerately poor.
Treatments for cancer typically includes surgery, chemotherapy, and/or radiation therapy. Although nearly 50 percent of cancer patients can be effectively treated using these methods, serious side effects that diminished quality of life are arisen from current therapies. Most chemotherapeutic drugs act on both normal and cancerous tissues. One of the challenges in treating cancerous tumors with chemotherapy is maximizing the killing of cancer cells while minimizing the healthy tissue damage. Depending on the administration route (e.g., intravenous) and nature of the drug (e.g., its chemical and pharmacokinetic properties), only a small fraction of the dose reaches the target cells; the remaining drug acts on other tissues or is rapidly eliminated.
To improve delivery efficiency and reduce toxicity to non-target cells, various strategies have been used to deliver drugs to specific sites in the human body. For example, the use of a toxin-conjugated monoclonal antibody in cancer treatment has been reported. The antibody provides selectivity for the aimed target, but there still remains the problem of interaction with non-target cells during the route to the intended site of action.
Currently, in order to develop novel targeting drugs, it is very important to find a biomarker of the tumor angiogenesis system. Various specific membrane proteins of the tumor angiogenesis system are highly expressed, such as integrin αvβ3, αvβ5 and vascular endothelial growth factor receptor 2. Additionally, it is well-known that the Arg-Gly-Asp (RGD) or Asn-Gly-Arg (NGR) peptides can specifically bind to tumor angiogenic endothelial cells.
However, tumor cells are highly variable, and the treated cancer cells become resistant to the treatment quickly. The current drugs and diagnosis agents for improving survival of cancer patients are ineffective.